Development and utilization of an infectious clone for porcine deltacoronavirus strain USA/IL/2014/026

Abstract

We report the generation of a full-length infectious cDNA clone for porcine deltacoronavirus strain USA/IL/2014/026. Similar to the parental strain, the infectious clone virus (icPDCoV) replicated efficiently in cell culture and caused mild clinical symptoms in piglets. To investigate putative viral interferon (IFN) antagonists, we generated two mutant viruses: a nonstructural protein 15 mutant virus that encodes a catalytically-inactive endoribonuclease (icEnUmut), and an accessory gene NS6-deletion virus in which the NS6 gene was replaced with the mNeonGreen sequence (icDelNS6/nG). By infecting PK1 cells with these recombinant PDCoVs, we found that icDelNS6/nG elicited similar levels of type I IFN responses as icPDCoV, however icEnUmut stimulated robust type I IFN responses, demonstrating that the deltacoronavirus endoribonuclease, but not NS6, functions as an IFN antagonist in PK1 cells. Collectively, the construction of a full-length infectious clone and the identification of an IFN-antagonistic endoribonuclease will aid in the development of live-attenuated deltacoronavirus vaccines.

Construction, Characterization and Application of Recombinant Porcine Deltacoronavirus Expressing Nanoluciferase

“…Recent studies have reported the construction of several reverse genetics systems for PDCoV via a T7-based system and a BAC-based system [ 38 , 39 ]. In contrast, combined with a one-step homologous recombination, we used the BAC-based system to more rapidly establish a reverse genetics system for PDCoV.…”

“…To establish a rapid and sensitive anti-PDCoV drug screening platform, a Nluc gene with many preponderant features, including small size, stability, and higher bioluminescence activity was designed to replace the NS6 gene due to its nonessential requirement for normal viral replication [ 38 ]. Recombinant PDCoV expressing Nluc was constructed on the basis of CRISPR/Cas9 technology, as described previously [ 41 ].…”

“…On the basis of reverse genetic systems, many studies have constructed recombinant virus bearing reporter genes, such as Green Fluorescent Protein (GFP), red fluorescent protein [RFP], or luciferase, with extensive advantages, including the analysis of viral characteristics, screening of antiviral drugs, and the detection of the viral host spectrum [ 34 , 35 , 36 , 37 ]. Recently, PDCoV infectious cDNA clone and reporter virus expressing GFP have been successfully constructed by RNA-launched and DNA-launched reverse genetic system [ 38 , 39 ]. However, the construction, characterization and application of PDCoV reporter virus expressing other reporter genes with better performance has not been reported until now.…”

An Updated Review of Porcine Deltacoronavirus in Terms of Prevalence, Pathogenicity, Pathogenesis and Antiviral Strategy

“…PDCoV NS6 interacts with RIG-I/MDA5, which in turn interferes with the binding of RIG-I/MDA5 to double-stranded RNA (dsRNA), resulting in the reduction of RLR-mediated IFN-β production ( 79 ). Whereas, Deng et al removed NS6 from the infectious clone of PDCoV and found that the deletion of NS6 did not affect the ability of the infectious clone virus to inhibit the type I IFN responses, implying that NS6 does not act as an IFN antagonist during PDCoV infection ( 80 ). PDCoV NS7a competes with tumor necrosis factor receptor-associated factor 3 (TRAF3) and IRF3 for binding to IκB kinase ε (IKKε) by interacting with the kinase domain and the scaffold dimerization domain of IKKε simultaneously, forming an antagonistic effect on RLR-mediated IFN-β production ( 81 ).…”

The recombinant pseudorabies virus expressing porcine deltacoronavirus spike protein is safe and effective for mice

“…The emerging coronavirus could cause widespread transmission among humans and animals, posing a major threat to human health and causing significant economic losses to the global livestock and trade industries. To date, at least six coronaviruses have been found to be pathogenic to pigs, They include porcine epidemic diarrhea virus (PEDV), porcine transmissible gastroenteritis virus (TGEV) and porcine acute diarrhea syndrome coronavirus (SADS-CoV), porcine respiratory coronavirus (PRCV), porcine transmissible gastroenteritis virus (TGEV), porcine haemagglutinative encephalomyelitis virus (PHEV) and porcine deltacoronavirus (PDCoV) [ 16 ]. Among them, as PDCoV is a newly emerged enteric pathogenic coronavirus that can cause severe diarrhea of piglets [ 3 ] in recent years, few studies have been conducted [ 17 ].…”